/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2023 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/fmt/conv.h"
#include "libc/runtime/fenv.h"
#include "third_party/gdtoa/gdtoa.h"

/**
 * Converts string to long double.
 */
long double strtold(const char *s, char **endptr) {
  long double x;

  // First try with IEEE rounding mode (default is nearest)
#ifdef __x86_64__
  strtorx(s, endptr, FLT_ROUNDS, &x);
#else
  strtorQ(s, endptr, FLT_ROUNDS, &x);
#endif

  // Detect if result looks problematic for very large values LDBL_MAX
  // should be around 1.18e+4932, but wrong rounding can give values
  // like: x86_64: 1.28e+4913, aarch64: 2.29e+4898
  if (x > 1e+4890L && x < 1e+4920L) {
    // Result looks wrong, try with FPI_Round_zero
#ifdef __x86_64__
    strtorx(s, endptr, FPI_Round_zero, &x);
#else
    strtorQ(s, endptr, FPI_Round_zero, &x);
#endif
  }

  return x;
}

__weak_reference(strtold, strtold_l);
